macos Sierra with CGA address?

Jeroen Massar jeroen at
Wed Dec 14 14:12:36 CET 2016

On 2016-12-14 13:26, Jeroen Massar wrote:
> On 2016-12-14 13:10, Jeroen Massar wrote:
>> [..]
>>> Actually, it is not a stable address as some have found out (read:
>>> anecdotal), they also change at re-install and there are a couple of
>>> other possibilities from what I recall.
>> From xnu-3248.60.10/bsd/netinet6/in6_ifattach.c:
> And after finding 10.12.1 sources (note that is not 10.12.2 which is out):
> There is a lot more SEND/CGA/"LLCGA" related stuff in here:
> eg:
> in6_ifattach_llcgareq has:
> 	if (nd6_send_opstate == ND6_SEND_OPMODE_DISABLED)
> 		return (ENXIO);
> Thus maybe one can disable it, if sysctl.conf has it disabled at
> boot...... lets find out :)

$ sysctl -a |grep opmode
net.inet6.send.opmode: 0
$ sysctl -a |grep opstate
net.inet6.send.opstate: 0
$ sysctl -a |grep maxif
net.inet6.ip6.maxifprefixes: 16
net.inet6.ip6.maxifdefrouters: 16

and have nice static or DHCP-assigned addresses without the silly

Thus summary:

$ cat /etc/sysctl.conf

First too disable silly random addresses (same /48, thus how many people
can that be);

net.inet6.send.opmode=0 disables the CGA-Link-Local-Address and thus
also the global random address.

Noting that this works on 10.12.2 (
root:xnu-3789.31.2~1/RELEASE_X86_64), but as per code likely also in
10.12 aka MacOS Sierra.

Iljitsch, maybe a good thing to update on: ?

that it can be disabled this way :)

  (now pushing out new sysctl.conf to all other boxes ;)

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